An external recording device for a computer mostly uses a magnetic disk as a recording medium. A standard magnetic disk has an outer diameter of 2.5 to 3.5 inches. A deposition process on a standard insulating substrate 2.5 to 3.5 inches in diameter for a magnetic disk is typically performed by a single-substrate-processing. The following two methods, for example, are used to apply a bias voltage on the insulating substrate during deposition. In one method, a conductive film (typically a base film) is deposited on the insulating substrate while being supported by a support tool at a particular position. Then, the portion supporting the insulating substrate is shifted to a different position and then a bias voltage is applied on the insulating substrate via the support tool and the conductive film while the supporting tool supports the portion on which the conductive film was deposited. In another method, a bias terminal is made to contact an end face of the insulating substrate after depositing the conductive film, and then the bias voltage is directly applied on the insulating substrate.
While the demand for a magnetic disk having a small diameter of 1.25 inches or less has gradually increased in recent years, the magnetic disk manufacturing apparatus has not changed. Although the same deposition device for the standard substrate 3.5 inches in diameter can be used to deposit layers on a small-diameter insulating substrate, the efficiency of a target to a product suffers, resulting in reduction in productivity.
When multiple-substrate-processing (for example, four-substrate-processing) small-diameter substrates to improve productivity, since the size of an objective product is smaller, the technique for shifting an insulating substrate proposed for example in JP-A-2001-216689 or counterpart U.S. Pat. No. 6,660,089 cannot be carried out. Thus, when multiple-substrate-processing is carried out, deposition is performed on an insulating substrate without applying a bias voltage on the substrate, or a base layer is first deposited, then a product is removed from a vacuum apparatus to shift and support the insulating substrate, and then deposition is performed again with the bias voltage applied in the vacuum apparatus.
In the former technique where no bias voltage is applied, an electromagnetic conversion property as a major property of a product is reduced. On the other hand, in the latter method, the insulating substrate needs to be temporarily removed from the vacuum apparatus and shifted to a different position. Consequently, quality of the product can be deteriorated by particles induced when the substrate is placed into or taken out from the vacuum apparatus.
Accordingly, there remains a need for a more efficient multiple-substrate-processing for small-diameter substrates without deteriorating the quality. The present invention addresses this need.